Female and inexperienced drivers have some difficulty parking their cars in parking lots, and may even cause collision. As such, many inexperienced drivers are under stress in connection with parking, and even tend to avoid driving.
In light of this, it has been proposed to mount sensors on the vehicle and automatically recognize a parking location so that the driver can park more conveniently. Sensors mounted on vehicles to automatically recognize the parking location are based on binocular stereo, motion stereo, light plane projection, ultrasonic waves, SGG (Short Range Radar), etc.
The method relying on binocular stereo or motion stereo to recognize an available parking space (and thus a target parking location) has a problem in that it does not work properly in the dark, and severe reflection from the vehicle surface makes it difficult to extract feature points. Particularly, black vehicles make it more difficult to extract feature points and obtain three-dimensional information regarding vehicles.
The method relying on light plane projection to recognize an available parking space (and thus a target parking location) employs a light plane projector to project a planar light source, and recognizes a light stripe created on the object. The light stripe is used to recognize vehicles on both sides of the available parking space and determine the target parking location. However, this method cannot be used in the daytime (i.e. when sunlight is strong), although it may supplement the above-mentioned method relying on binocular stereo or motion stereo in the nighttime or inside underground parking lots. Particularly, in the case of black vehicles, the amount of reflected light is insufficient, and the reliability of obtained three-dimensional information is degraded.
The method relying on ultrasonic sensors to recognize an available parking space (and thus a target parking location) is usually employed for parallel parking. Specifically, while the vehicle is moving, the distance to obstacles inside the parking slot is measured to recognize an available parking space (and thus the target parking location). However, this method has a problem in that, when already parked vehicles are not parallel with the moving direction, severe noise occurs and degrades the reliability of obtained three-dimensional information. Particularly, when intensive driving operations are necessary near the target parking slot (e.g. garage parking), the ultrasonic sensors are at an angle with regard to already parked vehicles, and the reliability of obtained three-dimensional information is low.
The method relying on SRR (Short Range Radar) to recognize an available parking space (and thus a target parking location) is usually employed for parallel parking, and is similar to the method relying on ultrasonic sensors. However, the variance of distance information is large, and noise is severe at distance-discontinuous points. Although this method provides distance information within a comparatively large FOV (Field of View), it is unsuited to recognizing the contour of a vehicle from points with severe electromagnetic reflection.